2020 Lake Hopatcong Water Quality Report released

January 27, 2021| Environment

By: Donna Macalle-Holly

Results of the 2020 Lake Hopatcong Water Quality Report were presented by Princeton Hydro Director of Aquatic Resources Dr. Fred Lubnow at the January meeting of the Lake Hopatcong Commission. Since 2018, the water quality monitoring program has been funded by the Commission. 

According to the report, “The current water quality monitoring program is valuable in terms of continuing to assess the overall “health” of the lake on a year‐to‐year basis, identifying long‐term trends or changes in water quality, and quantifying and objectively assessing the success and potential impacts of restoration efforts.  In addition, the in‐lake water quality monitoring program continues to be an important component in the evaluation of the long‐term success of the implementation of the phosphorus TMDL‐based Restoration Plan, which was approved by NJDEP in April of 2006.  The monitoring program also provides the data necessary to support the Foundation’s and Commission’s requests for grant funding to implement both watershed‐based and in‐lake projects to improve the water quality of Lake Hopatcong.  Finally, much of the data collected in 2020 will be used to assess the relative effectiveness of in‐lake and watershed‐based projects, designed to prevent or minimize the impacts of HABs in Lake Hopatcong.”

2020 Water Quality Report 

For previous water quality reports, click HERE. 

Below is a video summary of the report from Dr. Lubnow as well as a written summary from the Lake Hopatcong Commission. 
 

Summary

• Princeton Hydro has been graphing July surface water temperature data and has noted a statistically significant increase in water temperature.  Every year they monitor dissolved oxygen and water temperature relative to carry over and optimal habitat for brown trout.  Last season was the first where there was a temporary loss of optimal habitat, but also temporary loss in carryover habitat.  The loss of habitat occurred in July and was re-established in August.  Dr. Lubnow suggested that these are some of the impacts of climate change that waterbodies can expect to see as we experience an increase in temperatures.  
• Although HAB conditions improved in 2020, Dr. Lubnow notes that there were still high concentrations of chlorophyll-a at the mid-lake (deep water) station despite low phosphorus conditions.  Chlorophyll- a is produced by all plants and is an indicator of all species of algae concentrations in a waterbody.  By contrast, phycocyanin is only produced by cyanobacteria and can be used as an indicator of their concentration.  High chlorophyll-a concentrations at the mid-lake station tell us that algae is being produced in either near-shore areas and floating to mid-lake or originating deep in the water column and floating to the surface.  In 2020, the Lake Hopatcong Commission in partnership with the Lake Hopatcong Foundation was awarded a 319 -grant that will help determine how deep water contributes to HABs in Lake Hopatcong.  
• Each season Princeton Hydro calculates the amount of phosphorus removed through weed harvesting.  A total of 35 cubic yards of material was harvested in 2020, which equates to about six pounds of phosphorous.  This is considerably less than prior years when weed harvesting was conducted all summer.  In a normal year, the Commission could expect to remove about 200 pounds of phosphorus.  Dr. Lubnow concludes that this illustrates the value of weed harvesting not only to open waterways for recreational use and control invasive species, but it also helps to remove phosphorus from the water column.